Exhaust structure of engine

An exhaust structure of an engine, the exhaust structure comprising:

• an engine body in which a plurality of cylinders and a plurality of exhaust ports are formed, the plurality of cylinders being arranged in a predetermined cylinder arrangement direction, the plurality of exhaust ports extending from the plurality of cylinders;
• and an exhaust passage through which exhaust gas led out from the engine body flows, the exhaust structure of the engine, wherein
• when one side in an engine width direction, which is orthogonal to the cylinder arrangement direction and an up-down direction, is taken as an exhaust side, and an opposite side of the exhaust side is taken as an intake side, a plurality of exhaust port opening ends are open on a side surface of the engine body on the exhaust side, the plurality of exhaust port opening ends being outlets of the plurality of exhaust ports,
• the exhaust passage includes a plurality of independent passages, a collecting passage, a catalyst device, and a swirling part, the plurality of independent passages individually extending in the engine width direction from the plurality of exhaust port opening ends toward the exhaust side, the collecting passage being connected to end portions of the plurality of independent passages on a downstream side in a flow direction of exhaust gas, the exhaust gas that passes through the plurality of independent passages being collected in the collecting passage, the catalyst device being provided downstream of the collecting passage to purify the exhaust gas, the swirling part connecting the collecting passage to the catalyst device to cause the exhaust gas to swirl in the swirling part,
• the plurality of independent passages and the collecting passage have a shape that is bent in such a way as to bulge toward the exhaust side from the plurality of exhaust port opening ends and to extend downward, and
• the swirling part has a shape that causes the exhaust gas led out from the collecting passage to swirl about an axis extending along the cylinder arrangement direction.